Coaxial cable including at least one repeater

ABSTRACT

A coaxial cable comprising center steel wires, an inner conductor uniformly coated on the center steel wires, an outer tubular conductor, an inner insulator filled between the inner conductor and the outer tubular conductor, and an outer insulator coated on the outer surface of the outer tubular conductor. At least one unreflective section of wave absorbing material is provided in the inner insulator. A transmitted signal derived from the conductors of one side of the unreflective section is amplified by a wide band amplifier and applied to the conductors of the other side of the unreflective section. The wide band amplifier is embedded in the inner insulator and actuated by a dc difference between two opposed ends of a cut portion in one of the inner conductor and the outer conductor. Accordingly, a coaxial cable including at least one repeater is provided so as to have a uniform diameter.

United States Patent n91 Miya June 11, 1974 COAXIAL CABLE INCLUDING AT LEAST ONE REPEATER [75] Inventor: 'Kenichi Miya, Tokyo, Japan [73] Assignee: Kokusai Denshin Denwa Kabushiki Kaisha, Tokyo-to, Japan [22] Filed: Jan. 24, 1972 [21] Appl. No.: 219,957

[30] Foreign Application Priority Data Jan. 25, 1971 Japan 46-1986 Mar. 19, 1971 Japan 46-15077 Apr. 14, 1971 Japan 46-23135 [52] US. Cl 179/170 R, 179/170 J, 174/70 S [51] Int. Cl H04b 3/36, H04b 3/44, H04b 3/38 [58] Field of Search 179/170 T, 170 J, 170 R; 333/84 R, 97, 81 A, 22, 96; 174/70 S; 178/70 R [56] References Cited UNITED STATES PATENTS 2,610,250 9/1952 Wheeler.; 333/84 3,089,004 5/1963 Oswald 179/170J 3,560,889 2/1971 Suetake et a1. 333/22 3,582,576 6/1971 Karbowiak 179/170 R 3,610,812 10/1971 Furusawa ..333/84R Primary Examiner-Kathleen H. Claffy Assistant Examiner-Alan Faber Attorney, Agent, or FirmRobert E. Burns; Emmanuel J. Lobato; Bruce L. Adams 5 7 ABSTRACT applied to the conductors of the other side of the unreflective section. The wide band amplifier is embedded in the inner insulator and actuated by a dc difference between two opposed ends of a cut portion in one of the inner conductor and the outer conductor. Accordingly, a coaxial cable including at least one repeater is provided so as to have a uniform diameter.

2 Claims, 14 Drawing Figures COAXIAL CABLE INCLUDING AT LEAST ONE REPEATER This invention relates to a coaxial cable including at least one repeater.

A conventional submarine coaxial cable comprises a set of center steel wires having a strong tensile strength, an inner conductor uniformly coated on the center steel wires, an outer conductor of metal tube, an inner insulator of continuous solid dielectric filled between the inner conductor and the outer conductor, and an outer insulator of insulating tubular material coated on the outer surface of the outer conductor. If the above mentioned submarine coaxial cable is employed for providing an over-seas transmission line, submarine repeaters are inserted in the submarine coaxial cable at regular intervals of several tens kilometers for compensating transmission loss of the submarine coaxial cable. The conventional submarine repeaters are highly expensive. Moreover, since the conventional submarine repeaters are respectively inserted at cut positions of the regular intervals in a continuously produced submarine coaxial cable, laying of the conventional submarine cable is troublesome.

An object of this invention is to provide a coaxial cable including at least one repeater capable of readily providing an economical coaxial transmission line.

The principle, construction and operations of a coaxial cable of this invention will be clearly understood from the following detailed description taken in conjunction with accompanying drawings, in which:

FIGS. 1, 2 and 3 are longitudinal sections each illustrating a part of a coaxial cable of this invention including an unreflective section thereof;

FIG. 4 is a longitudinal section illustrating a part of a coaxial cable of this invention including a coupling used therein;

FIG. 5 is an elevation illustrating another example of a coupling used in a coaxial cable of this invention;

FIGS. 6A, 6B, 6C and 6D are side views illustrating elements used in a coupling shown in FIGS. 4 and 5;

FIGS. 7A and 7B are respectively a side view and an elevation illustrating a part of a coupling used in a coaxial cable of this invention;

FIGS. 8A and 8B are respectively a side view and an elevation illustrating a part of another coupling used in a coaxial cable of this invention; and

FIG. 9 is a longitudinal section illustrating a part of the unreflective section used in a coaxial cable of this invention.

With reference to FIG. 1, an example of a coaxial cable of this invention comprises a conventional coaxial cable and an unreflective section. The conventional coaxial cable comprises a set of center steel wires la having a strong tensile strength, an inner conductor 1 uniformly coated on the center steel wires 1a, an outer conductor 2 of metal tubing, an inner insulator 3 of solid dielectric filled between the inner conductor 1 and the outer conductor 2, and an outer insulator 4 of insulating tubular material coated on the outer surface of the outer conductor 2. Repeater means includes the unreflective section 5, two wave-absorbing materials 5-1 and 5-2 are provided between the inner conductor 1 and the outer conductor 2 and separated by an insulator 8 from each other. The outer conductor 2 is cut into two parts 2-1 and 2-2 at a center of the section 5 so as to separate the two parts 2-1 and 2-2 from each other with respect to a direct current. The two parts 2-1 and 2-2 are connected to each other by a capacitor 6 with respect to a high frequency alternating current. Moreover, the outer conductor 2 and the inner conductor 1 are connected to each other by a capacitor 7, so that the inner conductor 1 and the outer conductor 2 have the same potential at the center of the section 5 with respect to alternating currents in a transmission frequency band of the coaxial cable. In the absorbing material 5-1, a high-pass filter l3 and a low-pass filter 15a having the same cut-off frequency are provided. In the absorbing material 5-2, a high pass-filter 13a having the same cut-off frequency as the high-pass filter 13 is provided together with a low-pass filter 15 having the same cut-off frequency as the low-pass filter 15a. An amplifier 14 is provided at about a center of the section 5 for amplifying the high frequency currents including the transmission band of the coaxial cable. This amplifier 14 is actuated by a dc voltage between the two parts 2-1 and 2-2 of the cut portion of the outer conductor 2. An electric signal across terminals 9 and 9a of the conductors 2 and 1 are applied, through the high pass filter 13, to the amplifier 14. The amplified signal is applied, through the high pass filter 13a to terminals 10 and 10 a of the conductors 2 and 1. An electric signal across terminals 11 and 11a of the conductors l and 2 are applied, through the low-pass filter 15, to the amplifier 14, and the amplified signal is applied, through the low-pass filter 15a to terminals 12 and 12a of the conductors l and 2.

An electric signal travelling in the left-to-right direction is sufficiently attenuated in unreflective section 5, since the section 5 has a high transmission loss and an impedance viewed from the terminals 9 and 9a to the section 5 is equivalent to a condition terminated by a surge impedance of the coaxial cable. Mutual interference between the terminals 9 and 9a and the terminals 10 and 10a are substantially eliminated by a short circuit between the conductors l and 2 formed by the capacitor 7. Accordingly, the electric signal across the terminals 9 and 9a is applied, through the high-pass filter 13, the amplifier 14 and the high-pass filter 13a, to the terminals 10 and 10a.

An electric signal travelling in the right-to-left direction is sufficiently attenuated in the unreflective section 5 while the electric signal across the terminals 11 and 11a is applied, through the low-pass filter 15, the amplifier 14 and the low-pass filter 15a. Accordingly, the amplifier 14 performs bidirectional amplification. In other words, the example shown in FIG. 1 is a bidirectional repeater having the same diameter of the coaxial cable.

The unreflective section 5 can be realized by an insulator mixed with a conductive material having a high frequency loss (e.g. polyethylene mixed with carbon powder) or a non-conductive magnetic material (e.g. an oxide core). The length of the section 5 is from several centi-meters to about ten meters in consideration of a desired transmission characteristic in the transmission frequency band of about IO-mega Hz.

Elements of the filters 13, 13a, 15 and 15a and the amplifier 14 may be distributively disposed in the insulator (5-1, 8, 5-2) between conductors 1 and 2 at the unreflective section 5. However, if such elements are directly embedded in the insulator, these elements are liable to be affected by strain at an handling step of the coaxial cable or by a heat treatment at a fabrication step of the coaxial cable. To avoid the above defects, each block of the elements can be embedded in the insulator as shown in FIG. 1 after enveloping by a soft material 16, such as a soft rubber.

The amplifier 14 is a wide band semiconductor amplifier by way of example. In FIG. 1, the amplifier 14 is actuated by a dc difference between opposed ends of the two parts 2-1 and 2-2 of the outer conductor 2, which is employed for supplying a dc power from two ends of the coaxial cable by series-power supply. However, another conductor may be further provided for only the purpose of power supply.

Moreover, the inner conductor 1 may be employed for the power supply as shown in FIG. 2. In this example, the inner conductor 1 is divided into two parts l-l and 1-2 and insulated from the center wires 1a. The amplifier 14 is actuated by a dc difference between opposed ends of the two parts 1-1 and 1-2 of the inner conductor 1, which is employed for supplying a dc power from two ends of the coaxial cable by seriessupply in this case. In the example shown in FIG. 2, the filters 13, 13a, 15 and 15a and the amplifier 14 are embedded in a center insulator 8 between the conductors l and 2, while the unreflective section is divided into two parts 5-1 and 5-2 separated by the center insulator 8. A terminal of the part 1-1 of the inner conductor 1 provided at the left side of the section 5-1 is connected by a high frequency cable 17 to the filters 13 and 15a. On the other hand, a terminal of the part 1-2 of the inner conductor 1 provided at the right side of the section 5-2 is connected by a high frequency cable 17a to the filters 13a and 15. For simple illustration, connections for the ground which are connected from the filters 13, 13a, 15 and 15a and the amplifier 14 to the outer conductor 2 are eliminated.

The center steel wires 1a and the inner conductor 1 may be cut as shown in FIG. 3 for performing more reliable supply of dc power to the amplifier 14, if the cut ends of the center steel wires 1a and the inner conductor 1 are detached from each other and maintained in a separated condition by the use of coupling means including a coupling 20 of insulative material. In this example, a section 21 between positions 21 and 21a is a repeater which has the same outer diameter of the coaxial cable. Other parts are the same as the example shown in FIG. 2. Since the inner conductor 1 and the center steel wires la are completely separated into two parts 1-1 and 1-2 in this example shown in FIG. 3, signal transmission through the cut portion of the inner conductor 1 can be eliminated. In other words, bidirectional transmission is performed in the path: the cable 17, the high-pass filter 13, the amplifier 14, the highpass filter 13a and the cable 17a; and in the path: the cable 170, the low-pass filter 15, the amplifier 14, the low-pass filter 15a and the cable 17. Unnecessary travelling signals are completely absorbed by the parts 5-1 and 5-2 of the unreflective section 5.

With reference to FIGS. 4 6A, 6B, 6C and 6D, another example of the coupling 20 comprises a pair of branches or coupling means and 30a, four elongated branch rods 33a, 33b, 33c and 33d (not shown), a plurality of holders or spacing members 31a, 31b, 31c, 31d, 3le and 31]", and a plurality of supporters 32a, 32b, 32c, 32d and 32e. The inner conductor 1 and the center steel wires 1a of the coaxial cable are coupled to a center hole of each of the branches 30 and 30a shown in FIG. 6A in combination with an adhesive,

such as an epoxy resin. A pair of the branch lines 33a and 33b are coupled to two small holes of the branch 30 and held by holes of the holders 31b, 31d, 3lfshown in FIG. 6B and of the supporters 32a, 32b, shown in FIG. 6C, so that the branch lines 33a and 33b are separated from each other in parallel so as to be symmetrical with the axis of the coaxial cable. A pair of the branch lines 330 and 33d are coupled to two small holes of the branch 30a and held by holes of the holders 3le, 31c and 31a shown in FIG. 6B and of the supporters 32a, 32b, shown in FIG. 6C, so that the branch lines 33c and 33d are separated from each other in parallel so as to be symmetrical with the axis of the coaxial cable. In the above construction, the branch lines 33a and 33b are insulated from the branch lines 330 and 33d since these branch lines are arranged so as to divide a circle perpendicular to the axis of the coaxial cable into four equal parts. If necessary, the branch lines 33a, 33b, 33c, and 33d may be produced by an insulative material having a strong tensile strength.

In this example, a tensile force acting between a left part and a right part of the center steel wires of the coaxial cable is distributed to the inner insulator 3 through the branches 30 and 30a, branch lines 33a, 33b, 33c, and 33d, the holder 31a, 31b, 31c, 31d, 3le and 31e, and the supporters 32a, 32b, 32c, 32d and 32e, which are all fixedly embedded in the inner insulator 3. If the length of the branch lines 33a, 33b, 33c and 33d is extended, a tensile strength of the coaxial cable at this coupling section increases together with its flexibility. A frictional force acting between the inner insulator 3 and the branch lines 33a, 33b, 33c and 33d also withstands with the tensile force acting to the center steel wires la of the coaxial cable.

In an example of the coupling 20 shown in FIG. 5, a tensile force acting to the center steel wires la is maintained by a pair of the branch lines 33a and 33b and a pair of the branch lines 330 and 33d in combination with separators 34a, 34b and 34c of a hard insulating material shown in FIG. 6D. In other words, the separators 34a, 34b and 346 are employed for separating between the holders 31a and 31b, between the holders 31c and 31d, and between the holders 3le and 31f respectively. Accordingly, a tensile force acting to the center steel wires 1a of the coaxial cable is distributed to the inner insulator 3 as mentioned above and further maintained finally by the separators 34a, 34b and 340.

In the above example shown in FIG. 4 or 5, the holders 31 (31-3, 31-4) and the branch lines 33 are combined as shown in FIGS. 8A and 8B. In this case, each of the holders 31 is coupled with two branch lines 33. However, the number of the branch lines 33 coupled to each holder 31 may be increased. FIGS. 7A and 7B show an example in which three branch lines 33 are coupled to each holder 31.

With reference to FIG. 9, another example of one of two parts 5-1 and 5-2 of the unreflective section comprises resistive films 40 coated on the inner surface of the outer conductor 2 and the surface of the inner conductor l in addition to the surface of the small high frequency cable 17, magnetic films 41 coated on the resistive films 40, a wave absorbing material 42 provided around the inner conductor 1, and a capacitor 43 connected between the wave absorbing material 42 and the outer conductor 2. One end of the cable 17 is connected to the inner conductor 1 at the left side of the films 40 and 41, while the other end of the cable 17 is connected to the filters 13 and 15a as shown in FIGS. 1, 2 and 3.

A surge impedance W of a coaxial cable can be generally indicated as follows:

W= V r +jwLlg +jwC if a series resistance, an inductance, a conductance and a capacitance of a unit length of the coaxial cable are indicated respectively by notations r, L, g and C.

in accordance with the principle of this invention shown in FIG. 9, the resistance r is increased by the resistive films 40, such as tin oxide; and the impedance L is increased by the magnetic films 41. The conductance g and the capacitance C are substantially maintained at constant values. Accordingly, the surge impedance of the coaxial cable is effectively increased at the part shown in FIG. 9. Moreover, extremely weak signals passing through the part coated with the films 40 and 41 are absorbed into the wave absorbing material 42. If surfaces coated with the films 40 and 41 have creases the values of the resistance r and the inductance L can be further increased.

What I claim is:

l. A coaxial cable comprising center steel wires; an inner conductor coated uniformly on the center steel wires; an outer tubular conductor, an inner insulator filled between the inner conductor and the outer tubular conductor; an outer insulator coated on the outer surface of the outer tubular conductor; and repeater means comprising at least one unreflective section of wave absorbing material provided in the inner insulator, a wide band amplifier embedded in the inner insulator and actuated by a dc difference between two opposed ends of a cut portion in the inner conductor and the center steel wires for amplifying a transmitted signa] derived from one side of the unreflective section and for applying the transmitted signal to the other side of the unreflective section; two high pass filters having the same cut-off frequency and inserted respectively between the input of the amplifier and said one side of the unreflective section and between the output of the amplifier and the other side of the unreflective section, and two low pass filters having the same cut-off frequency as that of the two high pass filters and inserted respectively between the input of the amplifier and the other side of the unreflective section and between the output of the amplifier and said one side of the unreflective section, coup1ing means comprising insulating material and disposed at the cut portion for coupling said two opposed ends of the cut portion of the inner conductor and the center steel wires in a spaced-apart relationship comprising a pair of coupling members coupled respectively to said two opposed ends, a plurality of first parallel elongated branch rods coupled at one end portion thereof to one of the coupling members, a plurality of second parallel elongated branch rods coupled at one end portion thereof to the other of said coupling members, and means separating said first parallel branch rods from said second parallel branch rods including first spacing members and second spacing members fixed separately in the inner insulator and coupled to portions of said first plurality of parallel branch rods and said second plurality of parallel branch rods respectively to maintain the branch rods in a fixed spaced apart position with respect to each other.

2. A coaxial cable according to claim 1, in which the outer conductor and the inner conductor have at least one of resistive films and magnetic films on their surfaces adjacent to the inner insulator. 

1. A coaxial cable comprising center steel wires; an inner conductor coated uniformly on the center steel wires; an outer tubular conductor, an inner insulator filled between the inner conductor and the outer tubular conductor; an outer insulator coated on the outer surface of the outer tubular conductor; and repeater means comprising at least one unreflective section of wave absorbing material provided in the inner insulator, a wide band amplifier embedded in the inner insulator and actuated by a dc difference between two opposed ends of a cut portion in the inner conductor and the center steel wires for amplifying a transmitted signal derived from one side of the unreflective section and for applying the transmitted signal to the other side of the unreflective section; two high pass filters having the same cut-off frequency and inserted respectively between the input of the amplifier and said one side of the unreflective section and between the output of the amplifier and the other side of the unreflective section, and two low pass filters having the same cut-off frequency as that of the two high pass filters and inserted respectively between the input of the amplifier and the other side of the unreflective section and between the output of the amplifier and said one side of the unreflective section, coupling means comprising insulating material and disposed at the cut portion for coupling said two opposed ends of the cut portion of the inner conductor and the center steel wires in a spacedapart relationship comprising a pair of coupling members coupled respectively to said two opposed ends, a plurality of first parallel elongated branch rods coupled at one end portion thereof to one of the coupling members, a plurality of second parallel elongated branch rods coupled at one end portion thereof to the other of said coupling members, and means separating said first parallel branch rods from said second parallel branch rods including first spacing members and second spacing members fixed separately in the inner insulator and coupled to portions of said first plurality of parallel branch rods and said second plurality of parallel branch rods respectively to maintain the branch rods in a fixed spaced apart position with respect to each other.
 2. A coaxial cable according to claim 1, in which the outer conductor and the inner conductor have at least one of resistive films and magnetic films on their surfaceS adjacent to the inner insulator. 